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Scania: SCR and HCCI SCANIA IS PLOUGHING a lonely furrow
Page 46
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in the quest for cleaner truck technology.The Swedes, together with their American partner Cummins, have developed the XPI injection system which is already in use in the Euro-5 EGR generation of engines.The secret here is to increase peak injection pressures to as high as 2,400 bar, when other recent common-rail systems have reached peak pressures of no more than 1,6(K) bar.
"Now we've managed to reach Euro-5 with EGR, we are determined to do the same with Euro-6," says engine development manager Jonas Hofstedt."To achieve this, we will have to increase the capacity of the engine cooling system. We will not increase swept volume as we have just done."
Hofstedt is also clear about the future of the mighty Scania V8:-It will receive XPI and EGR to comply with Euro-6.To accommodate a larger radiator we will have to change the cab. Apart from that, maximum torque will increase even further."
Looking beyond Euro-6, Hofstedt foresees the introduction of another technical feature that Scania has tried to keep secret from journalists and competition: HCCI. With this system, air and fuel are premixed before entering the combustion chamber as if it were a petrol engine. However, it ignites due to the compression of the fuellair mix —just like a conventional diesel. Similar initiatives have recently been seen in the passenger car sector, but Scania developed its concept as long as four years ago. At that time, few people were yet discussing the need for an engine able to cope with fuel other than regular diesel, but Hofstedt stresses that HCCI will happily run on ethanol. He is also confident that in the post-Euro-6 era, exhaust gas legislation will focus on reducing CO, levels rather than particles or NOx,simply because these will already have been reduced to extremely low values. "By the year 2020, Stockholm will have a CO3-free public transport system," he adds.
Daf chief engineer Ron Borsboom can't wait for that era to get started:-Achieving Euro-6 will require a huge effort, while the result compared to Euro-5 will be very small, The increase in cleaning exhaust gases has no relation nowadays to the effort required."
One of the tricks Scania used to achieve Euro-5 with EGR was the introduction of a second cooling system.This 'dual-stage EGR' means that not only are exhaust gases being cooled by the fluid of the regular cooling system: there is also an air-cooled EGR cooler on top of the chargecooler.This technology was immediately patented by the Swedes, who realised that their competitors would have to deal with the same cooling problem in the era following Euro-5.